August 3, 2022 — Quantum computing, although still in its early days, has the potential to increase processing power by harnessing the strange behavior of particles at the smallest scales. Some research groups have already reported performing calculations that would take a traditional supercomputer thousands of years. In the long term, quantum computers can provide unbreakable encryption and simulations of nature beyond current capabilities.
An interdisciplinary research team led by UCLA including collaborators at Harvard University has now developed a new strategy to build these computers. While the current state of the art uses circuits, semiconductors and other electrical engineering tools, the team developed a game plan based on chemists’ ability to design the atomic building blocks that control the properties of larger molecular structures when they are placed. companion.
The findings, published last week in Nature Chemistry, could eventually lead to a leap in quantum processing power.
“The idea is, instead of building a quantum computer, to let chemistry build it for us,” said Eric Hudson, UCLA’s David S. Saxon Presidential Professor of Physics and corresponding author of the study. “We’re all still learning the rules for this kind of quantum technology, so this work is very sci-fi right now.”
The basic units of information in traditional computing are bits, each of which is limited to one of only two values. In contrast, a group of quantum bits – or qubits – can have a wider range of values, increasing the processing power of the computer. More than 1,000 normal bits are needed to represent just 10 qubits, while 20 qubits require more than 1 million bits.
That behavior, at the heart of quantum computing’s transformative potential, depends on counterintuitive rules that apply when atoms interact. For example, when two particles interact, they can be linked, or linked, so that measuring the properties of one determines the properties of the other. Entangling qubits is a prerequisite of quantum computing.
However, this excavation is weak. When qubits detect subtle changes in their environments, they lose their “mass,” which is necessary to implement quantum algorithms. This limits the most powerful quantum computers to less than 100 qubits, and keeping these qubits in a quantum state requires a lot of machinery.
To make quantum computing practical, engineers need to scale up the processing power. Hudson and his colleagues believe they have made a first step in the study, where theory guides the team to adapt the creation of molecules that protect quantum behavior.
Scientists have created small molecules that include calcium and oxygen atoms and act as qubits. These calcium-oxygen structures form what chemists call a functional group, which means it can be plugged into almost any other molecule while also imparting its own properties to that molecule.
The team showed that their functional groups maintained their desired structure even when attached to larger molecules. Their qubits can also withstand laser cooling, a key requirement for quantum computing.
“If we can bond a quantum functional group to a surface or some long molecule, we can control many qubits,” Hudson said. “It also has to be cheaper to raise, because the atom is one of the cheapest things in the universe. You can do as much as you want.”
In addition to its potential for next-generation computing, the quantum functional group can be a boon for fundamental discoveries in chemistry and the life sciences, for example by helping scientists discover more about the structure and function of various molecules and chemicals in the human body. .
“Qubits can also be very sensitive tools for measurement,” said study co-author Justin Caram, a UCLA assistant professor of chemistry and biochemistry. “If we can protect them so they can survive in complex environments like biological systems, we will be armed with a lot of new information about our world.”
Hudson said the development of a chemical-based quantum computer could realistically take decades and was not certain to succeed. Future steps include anchoring qubits to larger molecules, coaxing tethered qubits to interact as processors without unwanted signaling, and embedding them so they act as a system.
The project was seeded by a Department of Energy grant that gave physicists and chemists a chance to cut through discipline-specific jargon and speak a common scientific language. Caram also credits UCLA’s atmosphere of easy collaboration.
“This is one of the most intellectually fulfilling projects I’ve ever done,” he said. “Eric and I first met for lunch at the Faculty Center. It is born from fun conversations and being open to talking to new people.
UCLA postdoctoral researcher Guo-Zhu Zhu is the study’s first author. Other UCLA co-authors are doctoral students Claire Dickerson and Guanming Lao and faculty members Anastassia Alexandrova and Wesley Campbell.
The study was also supported by the National Science Foundation, the Army Research Office and the Air Force Office of Scientific Research.
Source: Wayne Lewis, UCLA